A digital pre-distortion apparatus is the device of compensating for the non-linearity of the power amplifier linearly by pre-distorting the digital signal input to the power amplifier. Such as pre-distortion apparatus is implemented with a digital circuit comprised of adder, multiplier, and Lookup Table (LUT) and an adaptive algorithm.
Here, the lookup table is a digital memory device with which the output signal is defined according to the input signal level and a digital circuit block appropriate for the operation of defining an output value depending on an input level.
The conventional digital pre-distortion apparatus uses multipliers for multiplying absolute value signals for the input signals having the non-identical number of delays. Typically, the use of multipliers increases the complexity of the circuit in hardware implementation. Unlike the case of using the lookup table, the conventional digital pre-distortion apparatus is disadvantageous in expandability because the same-structured multiplier has to be used repeatedly to express the sum of a plurality of terms.